Intracellular Mg2+ modulates the A-current and its blockage by catechol in isolated Lymnaea neurons.
The effects of intracellular Mg2+ (2-8 mM) upon the transient outward current (the A-current) under normal conditions and under catechol-induced blockage were studied in molluscan neurons by using the voltage-clamp and intracellular dialysis techniques. Identified giant Lymnaea stagnalis L. neurons were investigated at room temperature (20-22 degrees C). When applied intracellularly, Mg2+ caused both time- and dose-dependent shifts of the voltage dependence of the steady-state activation and inactivation of the A-current to more negative membrane potentials. Upon external application, catechol suppressed (5-6 mM) or eliminated (9-10 mM) the A-currents, slowed down the current decay and shifted the activation and inactivation curves to more positive membrane voltages. Intracellular Mg2+ decreased the blocking ability of extracellularly applied catechol, whereas catechol antagonized the Mg2(+)-induced negative shift of the steady-state activation and inactivation curves of the A-currents.
Erdélyi
L
L
Department of Comparative Physiology, Attila József University, Szeged, Hungary.
Ilyin
V I
VI
Lozovaya
N A
NA
Vulfius
C A
CA
D000818:Animals; D002396:Catechols / Q000494:pharmacology*; D066298:In Vitro Techniques; D007700:Kinetics; D008195:Lymnaea; D008274:Magnesium / Q000494:pharmacology / Q000502:physiology*; D008564:Membrane Potentials / Q000187:drug effects; D009474:Neurons / Q000187:drug effects / Q000502:physiology*
D002396:Catechols; D008274:Magnesium; C034221:catechol